[290] Mt. W. Contr., in press.

[291] J. Op. Soc. Am., 8, 609, 1924.

[292] Payne, Proc. N. Ac. Sci., 11, 192, 1925.

[293] Menzel, H. C. 258, 1924.

[294] Chapter VII, [p. 113].

[295] Maury, H. A., 28, 79, 1900.

[296] Russell, Mt. W. Contr., in press.

[297] H. C. 258, 1924.

[298] Chapter IX, [p. 123].

[299] loc. cit.